Different device types, such as n-type metal oxide semiconductor (NMOS) devices or p-type metal oxide semiconductor (PMOS) devices, typically require substantially different compositions of equivalent layers in their respective gate stacks to achieve the desired threshold voltages necessary to operate each device. For example, different devices may require different compositions of one or more of a high-k dielectric layer or a metal layer in their respective gate stacks to achieve threshold voltages necessary to operate each device. The requirement of different layers having different compositions typically requires multiple masking and deposition steps to deposit each layer, adding to the cost and time of manufacturing.
Accordingly, the inventors have developed the improved methods of forming semiconductor devices.